1. Field of the Invention
The present invention relates to means for sealing within a flow conduit for controlling fluid flow therein. In particular, the invention comprises a packer for sealing against a surrounding well conduit. The invention is particularly, though not exclusively, adapted to hydraulic set packers operated by fluid pressure applied via the tool mandrel and its supporting tubing string.
2. Description of the Prior Art
One of the problems associated with many conventional packers is that of leakage due to high pressures within the well conduit being sealed. For example, in a typical hydraulic set packer, if the pressure within the well exceeds the effective hydraulic setting pressure, leakage past the packer seal may occur. There is need for a relatively simple and economical packer which will effectively seal against such leakage without the application of excessive internal setting pressure and, in particular, one in which the seal will be tightened in its set position upon the presence of well pressure differentials across the seal in either longitudinal direction.
Another problem associated with the use of conventional packers is that the seal, being generally in an exposed and vulnerable position on the exterior of the tool, is subject to damage. For example, when the tool is being run into the well, it may be damaged by contact with internal obstructions or irregularities in the well conduit. Rapid lowering of the packer increases the likelihood of such damage and may also create a swabbing effect which can itself damage the seal and/or cause premature setting of the packer. Another occasion for seal damage may occur after the tool has been lowered into the desired position, but before it has been set, due to the abrading effects of sand and other material in the well fluid which may be circulated about the seal. Thus, in the past it has frequently been necessary to lower the packer into the well slowly to avoid such damage.
Another disadvantage of many conventional hydraulic set packers is that, in order to provide an adequate stroke for the piston of the seal actuator, the packer must be made relatively long and is consequently difficult and sometimes impossible to maneuver in tortuous well conduits. Attempts to shorten the overall packer length made at the expense of the size of the seal may result in reduced sealing effectiveness.
There is therefore a need for an improved packer, and in particular for a hydraulic set packer, which will alleviate these and other problems in conventional prior art tools.